6.	Income Taxes

The Company’s effective income tax rate for the three-months ended March 31, 2018 was 19.7%. The effective income tax rate reflects the effect of federal and state income taxes and the impact of differences in book and tax accounting arising from the net permanent benefits associated with the statutory depletion deduction for mineral reserves. For the three-months ended March 31, 2018, the effective income tax rate also reflects two discrete events: a favorable impact of $1,325,000, or 1,060 basis points, related to the vesting and exercise of stock-based compensation awards and an unfavorable impact of $1,097,000, or 880 basis points, related to an estimate of the transition tax on undistributed foreign earnings, a provision of the Tax Cuts and Jobs Act of 2017 (2017 Tax Act). The enactment of the 2017 Tax Act reduced the federal statutory corporate income tax rate from 35% to 21% beginning in 2018. Therefore, the effective income tax rate of 25.6% for the three-months ended March 31, 2017 is not comparable.

The Securities and Exchange Commission issued Staff Accounting Bulletin No. 118 (SAB 118) to address situations when a registrant does not have the necessary information available, prepared or analyzed (including computations) in reasonable detail to complete the accounting for certain income tax effects of the 2017 Tax Act. As such, due to the timing of the enactment date and the Company’s reporting periods, the Company recognized provisional amounts for the remeasurement of deferred tax assets and liabilities as of December 31, 2017 and transition tax on undistributed foreign earnings as of March 31, 2018, and continues to analyze and assess other provisions of the 2017 Tax Act. In accordance with SAB 118, the Company may record additional provisional amounts during the measurement period not to extend beyond one year of the enactment date and expects the accounting to be complete when the Company’s 2017 U.S. corporate income tax return is filed in 2018. Any future measurement period adjustments will be recognized as income tax expense or benefit in 2018.

The Company records interest accrued in relation to unrecognized tax benefits as income tax expense. Penalties, if incurred, are recorded as operating expenses in the consolidated statements of earnings and comprehensive earnings.